In recent times, a backlight device in which an LED light source is disposed at side sections of a light guide body having a bar shape is disclosed. FIG. 1 is an exploded perspective view showing a backlight device of the related art, and FIG. 2 is a perspective view showing a light guide bar serving as a major part of FIG. 1. The backlight device using the light guide bar of the related art includes a reflection plate 20 and a plurality of light guide bars 30 disposed in a cover bottom 10 at equal intervals, and LEDs 40 serving as light sources disposed at both side sections of the light guide bar 30. A diffusion plate 50 and various optical sheets 60 are disposed over the light guide bar 30. A guide panel 70 is fastened to the cover bottom 10.
The light guide bars 30 have one side surface or both side surfaces in a longitudinal direction thereof that constitute a light incident surface through which light of the LED 40 enters, and an upper surface and both side surfaces that constitute a light emission surface through which light is emitted. Lower surfaces of the light guide bars 30 constitute a reflection surface configured to reflect light scattered therein upward. A light reflection pattern 31 configured to efficiently reflect light to improve brightness is formed at the lower surface.
However, the light guide bar 30 having such a structure concentrates most of the light to the upper surface due to the light reflection pattern 31 formed at the lower surface and emits the concentrated light. In this case, while optical characteristics over the light guide bar 30 have high brightness in a region in which the light guide bar 30 is disposed, a relative dark area is generated in a space between the light guide bars 30. This difference in light and shade according to a position of the light guide bar 30 may cause a decrease in optical characteristics such as the entire brightness of the backlight device, brightness uniformity, and so on.
In particular, the decrease in appearance caused by the light guide bar becomes serious as the backlight device is slimmed in recent times. In order to prevent this, while a method of narrowing a gap between the light guide bars 30 is proposed, in this case, a relatively large number of light guide bars 30 are used to increase manufacturing costs and power consumption of the backlight device. In addition, while a method of increasing a gap between the light guide bar 30 and the diffusion plate 50 is also provided, brightness is decreased and slimming of the backlight device is prohibited.